This invention relates to archery bows, and, more particularly, to eccentrics for archery bows.
Archery bows, particularly compound archery bows, have evolved considerably in recent times. Compound archery bows rely on a mechanical advantage provided by one or more cams with interconnecting cables which allow the archer to draw the compound archery bow beyond the peak draw weight until a let off draw weight is achieved. The energy stored in the limbs of a compound archery bow when fully drawn is therefore greater that the energy stored in the limbs of a traditional archery bow where the archer must hold the peak draw weight until the arrow is launched. The let off of a compound archery bow allows the archer to hold substantially less than the peak draw weight (typically 50% to 80% of the peak draw weight) when aiming and shooting the archery bow.
Efforts are continually being made to improve all aspects of performance of a compound archery bow. Many variables affect the performance of a compound archery bow, including without limitation the axle-to-axle length, the brace height, the peak draw weight, the configuration of the eccentric cam(s), the length of the bowstring, and many others. Design factors of particular importance to consumers include draw length and draw weight adjustability, as well as percentage of let off relative to the peak draw weight.
The advantages of single-cam archery bows are well known. Single cam archery bows tend to shoot more quietly than dual-cam archery bows and are easier to maintain, since there is only one eccentric or cam. In addition, single-cam archery bows do not experience the timing problems which can plague dual-cam archery bows, where both of the cams or eccentrics must rotate precisely in unison to achieve optimal accuracy.
A common problem associated with traditional compound archery bows is that every time the compound archery bow needs certain types of adjustments, such as changing the draw length, a bow press is generally required to effect such changes. In using a bow press, the archery bow is anchored to the bow press and the limbs are tensioned so that the bowstring becomes relaxed and adjustments to the mechanical features of the archery bow and the eccentric(s) can be made.
Bow presses are cumbersome and difficult to use. In addition, many archers also participate in bowhunting, an activity that does not lend itself well to use of a bow press. While portable bow presses exist, these bow presses are nonetheless cumbersome to take and awkward to use in the field. Bow presses, even portable ones, also take up cargo space in situations where cargo space is placed at a high premium.
One of the more common adjustments that archers desire to make to their archery bows relates to the percent let off of the peak draw weight. Traditionally, one of the only ways to change the percent let off of a compound archery bow has been to change the configuration of the eccentric(s) or cam(s). The peripheral configuration of the eccentric or cam generally dictates the archery bow""s let off relative to the peak draw weight of the bow. Changing the configuration of the cam or eccentric will also, however, change many other performance aspect of the compound archery bow, including the draw length of the bow.
Still another problem with compound archery bows relates to the noise created when the cables and/or bowstring slap against the portions of the eccentric(s) or idler when the archery bow is at full draw. Because game animals have tremendous hearing ability, any noise from the compound archery bow must be minimized and preferably eliminated all together when bowhunting.
In view of the foregoing, there is a need to develop an archery bow that is highly adjustable, both with respect to draw length and percent let off relative to the peak draw weight. There is a further need to reduce or eliminate audible sounds that result from drawing a compound archery bow.
It is a primary object of the present invention to provide an adjustable eccentric for a compound archery bow.
Another object of the present invention is to provide an eccentric for a compound archery bow with a let-off adjustment module.
Still another object of the present invention is to provide an eccentric for an archery bow that will allow adjustments to be made to the draw length and percent let off without the need of a bow press.
Another object of the present invention is to provide an eccentric for an archery bow comprising a let-off adjustment module that pivots between two let-off positions.
Yet another object of the present invention is to provide a dampening device coupled to the eccentric for reducing noise upon launching an arrow from the archery bow.
The foregoing objects of the present invention are achieved by a novel adjustable eccentric for a compound archery bow. The eccentric includes a let-off adjustment module that pivots between two let-off positions: in a preferred embodiment between a 65% let-off position and an 80% let-off position. The let-off adjustment module can be adjusted without a bow press; that is, while the archery bow is in a rest position and the string is tensioned between the two archery bow limbs. Adjusting the module between a first let-off position and a second let-off position effectively changes the distance between the cable and the pivot axis of the eccentric at full draw, which changes, in turn, the let off. The eccentric is also adjustable to change the draw length within a range of five inches. Draw length adjustments can be made in one-half inch increments. A dampening device is further secured to the eccentric at a location on the cable take-up groove to absorb and reduce noise generated upon drawing the archery bow prior to launching an arrow.
Other objects, features, and advantages of the invention will become apparent from the following detailed description of the invention with reference to the accompanying drawings.